Switching Channel Pass Receive Filter

Abstract

A switchable channel-pass filter may be used on the receiver path of a multichannel radio system. The channel-pass filter may have several filter elements that may be switched in and out of the circuit to narrowly filter the incoming signal outside of the channel spectrum, which may be significantly narrower than the normal spectrum of the radio. The switchable channel-pass filter may be downstream from at least one low noise amplifier and may operate within the intermediate frequency area of the receiver path. Common applications for the switchable channel-pass filter may be IEEE 802.11 and IEEE 802.16 radio systems.

1 . A radio comprising:
 an antenna input;   a radio controller;   a receive path comprising:
 an amplifier; 
 a switchable filter network downstream from said amplifier and comprising a plurality of filters, at least one of said filters having a range less than the operating range of said radio, said switchable filter network being switchable by said radio controller. 
   
   
   
       2 . The radio of  claim 1 , at least one of said plurality of filters having a range at least as great as said operating range of said radio. 
   
   
       3 . The radio of  claim 1 , said at least of said plurality of filters being adapted to filter signals outside a single channel range. 
   
   
       4 . The radio of  claim 1  substantially conforming to IEEE 802.11. 
   
   
       5 . The radio of  claim 4  further comprising:
 a first of said plurality of filters adapted to pass channel 1 signals and filter at least a portion of channel 6 signals;   a second of said plurality of filters adapted to pass said channel 6 signals and filter at least a portion of said channel 1 signals and channel 11 signals; and   a third of said plurality of filters adapted to pass said channel 11 signals and filter at least a portion of said channel 6 signals.   
   
   
       6 . The radio of  claim 4  further comprising:
 a fourth of said plurality of filters being a short.   
   
   
       7 . The radio of  claim 4  further comprising:
 a fourth of said plurality of filters being adapted to pass all signals within said operational range of said radio.   
   
   
       8 . The radio of  claim 1  substantially conforming to IEEE 802.16. 
   
   
       9 . A method comprising:
 setting a switchable filter network to a first filter having a range at least as great as the operational range of a multichannel receiver;   receiving a signal on said multichannel receiver;   determining that said signal is on a first channel;   selecting a second filter within said switchable filter network, said second filter having a range less than said operational range and at least as great an operational range as said first channel; and   setting said switchable filter network to said second filter.   
   
   
       10 . The method of  claim 9 , said switchable filter network being located downstream from a receive amplifier on a receive circuit of said multichannel receiver. 
   
   
       11 . The method of  claim 9  substantially conforming to IEEE 802.11. 
   
   
       12 . The method of  claim 11  wherein:
 said first channel is channel 1; and   said second filter is adapted to pass channel 1 signals and filter at least a portion of channel 6 signals.   
   
   
       13 . The method of  claim 9  substantially conforming to IEEE 802.16. 
   
   
       12 . A radio receive path comprising:
 an amplifier;   a switchable filter network downstream from said amplifier and comprising a plurality of filters, at least one of said filters having a range less than the operating range of said radio.   
   
   
       13 . The radio receive path of  claim 12 , at least one of said plurality of filters having a range at least as great as said operating range of said radio. 
   
   
       14 . The radio receive path of  claim 12 , said at least of said plurality of filters being adapted to filter signals outside a single channel range. 
   
   
       15 . The radio receive path of  claim 12  substantially conforming to IEEE 802.11. 
   
   
       16 . The radio receive path of  claim 15  further comprising:
 a first of said plurality of filters adapted to pass channel 1 signals and filter at least a portion of channel 6 signals;   a second of said plurality of filters adapted to pass said channel 6 signals and filter at least a portion of said channel 1 signals and channel 11 signals; and   a third of said plurality of filters adapted to pass said channel 11 signals and filter at least a portion of said channel 6 signals.   
   
   
       17 . The radio receive path of  claim 16  further comprising:
 a fourth of said plurality of filters being a short.   
   
   
       18 . The radio receive path of  claim 16  further comprising:
 a fourth of said plurality of filters being adapted to pass all signals within said operational range of said radio.   
   
   
       19 . The radio receive path of  claim 12  substantially conforming to IEEE 802.16.